Method for a Mobile Station to Roam Among Networks of Different Criteria

ABSTRACT

The present invention provides a method for a mobile station to roam among networks of different criteria. It includes: recording user information in number portability database, when a mobile station processes location registration, the home location register of the current roaming network processes an inter-network number portability request, then returns a location register response message; when the mobile station initiates a call, the call flow is the same as the current initiation flow; when the mobile station ends a call, the initiation switch center obtains the inter-network roaming state of the mobile station, then processes call transfer. The present invention expediently realizes inter-network roaming among networks of different criteria, especially the inter-network roaming between the GSM network and the CDMA network, need not realize complicated IIF protocol conversion function, reduces infection to the current network stability, and realizes number portability when the subscriber roams among different networks; it uses a simple private interface between the number portability database and the home location register, does not depend on the standards of GSM MAP and CDMA MAP and does not infect the absolute development of the two networks.

FIELD OF THE INVENTION

The present invention relates to an interconnection andintercommunication technology among mobile communication networks ofdifferent criteria, and specifically, to a method for a mobile stationto roam between the GSM network and CDMA network.

BACKGROUND OF THE INVENTION

In the field of mobile communication, the GSM network and CDMA networkare two representative networks based on different technologicalstandards, the developments of the two networks are separated from eachother, but interconnection and intercommunication among networks ofdifferent criteria is desired more and more, accordingly, theinterconnection and intercommunication technology among networks ofdifferent criteria is developed.

An representative interconnection and intercommunication technology is anetwork interconnection technology based on an Interworking andInteroperability Function (short for IIF) entity, which is proposed by3GPP2 (3^(rd) Generation Partnership Project 2) Organization. Byintroducing the IIF entity, the technology implements the protocolconversion between GSM Mobile Application Part (short for MAP) and CDMAMAP, thereby combining the GSM network and CDMA network. As for a GSMsubscriber who roams to the CDMA network, the IIF entity acts as a HLR(Home Location Register) in the CDMA network and a VLR (Visited LocationRegister) in the GSM network for the subscriber; and as for a CDMAsubscriber who roams to the GSM network, the IIF entity acts as the HLRin the GSM network and the VLR in the CDMA network for the subscriber.

Another interconnection and intercommunication technology adopts thesolution of mobile service node (short for MSN), and in this solution,MSN is used as a connecting device between the CDMA wireless accessnetwork and the GSM core network. As for a GSM subscriber who roams tothe CDMA network, MSN acts as the MSC (Mobile Switching Center) in theGSM network, and shields the CDMA wireless access network, therefore,implements the conversion between the CDMA1x IOS (InteroperabilitySpecification) protocol and the GSM MAP protocol.

Comparison is made between the above two technical solutions and it canbe seen that the network interconnection technology based on IIF entitydoes not need the existing GSM network and CDMA network to provide a newprotocol support, the IIF entity bridges the communication between theCDMA core network and GSM core network, and shields the infection ofinter-network roaming to a home network; on the other hand, the solutionbased on MSN needs to change the existing network a lot. In addition,both of the above two technical solutions are required to be compatiblefor the protocol and standard of the two networks, the IIF entity shouldcomplete complex protocol conversion, and the MSN also needs to provideprotocol support for a heterogeneous network, then it is relativelycomplex to carry out the above two solutions.

Besides the above two solutions, Chinese patent application No.02104295.0, entitled “A Method for Implementing SignalingIntercommunication Between the GSM network and CDMA network” alsoprovides a mechanism for solving the interconnection andintercommunication between networks. In the method, a communicationinterface between the HLR in the GSM network and the HLR in the CDMAnetwork is established first, and the inter-network roaming of a user issupported through the interaction of inner message between the GSM HLRand CDMA HLR. A mobile user who supports double modes keeps a piece ofsubscriber data at the GSM HLR and CDMA HLR respectively, and the mobileuser numbers in the two pieces of subscriber data serve as a forwardingnumber for each other. In the process of location registration, aprocedure of sending the roaming state of the current network where theuser resides to the non-current network is added; and in the flow ofobtaining called location information, a step of judging the currentnetwork where the user resides is added. Then the HLR determines,according to the roaming state of the user, to return a normal routingnumber or a mobile user number of the opposite network recorded in aforwarding number field. It is not necessary for this solution to add inexisting networks a IIF entity which performs complex translationfunction, and is easy to implement, however, the mobile user needs touse different numbers in the GSM network and the CDMA networkrespectively, such that Number Portability (Number Portability, shortfor NP) as the user roams among networks cannot be implemented, andbesides, the forwarding property of the user is also influenced.

NP is a technology for a user to go on use an original number after theuser changes a service provider, wherein the Number Portability Database(short for NPDB) is a key entity for implementing NP function, and isused for recording the corresponding relation between the directorynumber of the user and the location routing number of a service network.When the user changes the service provider, the location routing numberrecorded in the NPDB should be amended, too. When a call enters aningress switch, the ingress switch sends search information to the NPDBfor searching the location routing number; the NPDB returns the locationrouting number in the new service network of the called user to theingress switch, and guides the ingress switch to connect the call to thecurrent service network of the called user. NP technology is developedfrom fixed switch network, and currently, its application has expandedto the mobile switching field, but the technology is generally used forPN among different service providers in the networks of the samecriterion. US patent application No. 20020052211, entitled “Method forProviding Number Portability of Mobile Phone”, proposes a NP solutionthat a NPDB which supports multiple network search interfaces is used innetworks of different criteria. In this method, the NPDB supports thesearch request initiated by networks of multiple criteria, and canreturn the location routing number of the current service network of thecalled user to the switches of the networks of multiple criteria,thereby supporting the carrying of the number by the user to networks ofdifferent criteria. However, the NPDB of the invention does not have thecapability of managing inter-network roaming of the mobile station.

SUMMARY OF THE INVENTION

The technical problem the present invention aims to solve is to providea method for a mobile station to roams among networks of differentcriteria, so as to solve the problem of interconnection andintercommunication among networks of different criteria, especiallyamong the GSM network and CDMA network, and meanwhile, to implement NPwhen the user roams among different networks.

The method for a mobile station to roams among networks of differentcriteria according to the present invention comprises:

record user information in NPDB, wherein the user information includes adirectory number and a location routing number of the mobile station, amobile station identifier that the mobile station signs at network 1, amobile station identifier that the mobile station signs at network 2,and current NP state of the mobile station;

when the mobile station conducts location registration, the HLR of thecurrent roaming network conducts an inter-network NP request operation,then returns a location registration response message;

when the mobile station initiates a call, the call flow is the same asthe current initiation flow;

when the mobile station ends the call, the initiation switching centerobtains the inter-network roaming state of the mobile station, and thenconducts a call connection operation.

In the present invention, the flow that the mobile station conductslocation registration specifically comprises:

step 1, the switching center of the current roaming network initiates alocation registration request to the HLR of the present network afterreceiving the location registration request initiated by the mobilestation;

step 2, the HLR of the current roaming network sends an inter-network NPrequest message to the NPDB;

step 3, the NPDB judges whether it is necessary to notify the originalroaming network of the mobile station to logout the registration; and ifnot necessary, the flow proceeds to step 5;

step 4, if it is necessary to notify the original roaming network of themobile station, the NPDB sends an inter-network NP logout requestmessage to the HLR of the original roaming network, then the HLR in turnsends a logout registration message to the switching center of theoriginal roaming network; after receiving the logout registrationresponse message returned by the switching center of the originalroaming network, the HLR of the original roaming network returns aninter-network NP logout response message to the NPDB;

step 5, the NPDB records the current NP state of the mobile station, andsends an inter-network NP response message to the HLR of the currentroaming network of the mobile station; and

step 6, the HLR of the current roaming network returns a locationregistration response message to the switching center of the presentnetwork.

The procedure that the mobile station ends the call specificallycomprises: after receiving the call request, the initiation switchingcenter queries the NPDB for the location routing number of the calleduser; the NPDB returns the location routing number to the initiationswitching center, and the initiation switching center completes the callconnection according to the location routing number.

The procedure that the mobile station ends the call further comprises:after receiving the call request, the initiation switching center checkswhether the called user is a potential NP user; if not, process as anormal call flow; and if the user is a potential NP user, the subsequentsteps are executed

The initiation switching center judges whether the user is a potentialNP user according to the directory number of the mobile station, whichis specifically as follows: if the directory number of the mobilestation is within the range of a set inter-network roaming user number,then the user is considered as the potential NP user, or else, the useris not the potential NP user.

Through functional expansion of and simple amendment to the NPDB,switching center, and HLR of the existing network, the present inventionrealizes inter-network roaming among the networks of different criteriaexpediently, especially inter-network roaming between the GSM networkand CDMA network; it is not required for the present invention torealize complicated IIF protocol conversion function, thus reducesinfection to the stability of the current network, and meanwhile,realizes NP in case of inter-network roaming. Moreover, it uses a simpleprivate interface between the NPDB and HLR, which does not relay on thestandards of GSM MAP and CDMA MAP, as a result, it will not infect theabsolute development of the two networks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the structure of the network used in themethod according to the present invention;

FIG. 2 is a flowchart of the location registration conducted by themobile station of the method according to the present invention

FIG. 3 is a flowchart shows that the mobile station is called whenroaming in the present network of the method according to the presentinvention; and

FIG. 4 is a flowchart shows that the mobile station is called whenroaming among different networks of the method according to the presentinvention.

EMBODIMENTS FOR CARRYING OUT THE PRESENT INVENTION

Hereinafter, the present invention will be described in detail withreference to the drawings and embodiments thereof.

The method according to the present invention is used for inter-networkroaming among networks of different criteria. In the followingembodiment, network 1 is the GSM network, network 2 is the CDMA network,and the mobile station is one that supports networks of differentcriteria. As shown in FIG. 1, the switching center, i.e. MSC/VLR, aswell as the HLR in the GSM network and the CDMA network respectivelyconnect to the NPDB, wherein the signaling interface between the HLR andthe NPDB is newly added, and the GSM network and the CDMA network areconnected through their respective gateway office GMSC. In the network,the HLR further cooperates with the NPDB to realize inter-network NPmanagement of a double module mobile user in addition to complete itsbasic functions in respective networks, comprising: adding a process ofinitiate a NP request signaling to the NPDB during the locationregistration procedure of the mobile station, adding a process of sentan inter-network NP deactive signaling to the NPDB during the power offprocedure of the mobile station, and adding a process of initiate aninter-network NP cancel signaling to the NPDB. The NPDB mainly realizesthe management over user inter-network NP, comprising: responding to theinter-network NP request signaling and inter-network NP deactivesignaling initiated by the HLR of the current roaming network of themobile station, and initiating inter-network NP cancel signaling to theHLR of the original roaming network. In addition, the MSC should supportNP function, and can search the NPDB for the location routing number.

Before inter-network roaming, the double module mobile user needs tosign a piece of user information with the GSM network and the CDMAnetwork respectively, and in the two networks, directory numbers of theuser are the same. Thereafter, the user information is recorded andstored in the NPDB, including the directory number of the mobilestation, the location routing number, the mobile station identifier ofthe mobile station signed at the GSM network, the mobile stationidentifier of the mobile station signed at the CDMA network, and currentNP state of the mobile station, wherein the location routing number isthe routing number of the gateway office of the GSM network or the CDMAnetwork; and the NP state comprises the roaming network and active stateof the mobile station.

The method for realizing inter-network roaming according to the presentinvention comprises: the location registration flow of the mobilestation, the power off flow of the mobile station, the initiation flowof the mobile station, and the call ending flow of the mobile station.

When the mobile station conducts location registration, for a doublenetwork roaming user, the HLR of the current roaming network adds aprocess of initiate a inter-network NP request to the NPDB, if the NP ofthe mobile station in the heterogeneous network recorded in the NPDB isin an active state, then an inter-network NP cancel message is sent tothe original roaming network; after receiving the inter-network NPcancel message, the HLR of the original roaming network sends a logoutregistration message to the MSC/VLR of the original roaming network ofthe mobile station, indicating the user has left.

When the mobile station powers off, the HLR of the current roamingnetwork sends a inter-network NP deactive message to the NPDB, and theNPDB updates the NP of the mobile station in the network as the deactivestate.

The initiation flow of the mobile station is the same as the existingone.

When the mobile station ends the call, the initiation MSC searches theNPDB for the location routing number, and thus obtains the inter-networkroaming state of the mobile station. If the current roaming network ofthe mobile station is the same as that of the caller, the initiation MSCrequests the HLR of the present network for a roaming number, andcompletes the call connection; otherwise, the initiation MSC connectsthe call to the gateway office GMSC of the current roaming network ofthe mobile station according to the location routing number returned bythe NPDB, then the gateway office of the roaming network continues torequest the HLR of the roaming network for the roaming number, andcompletes the call connection of the mobile station after itsinter-network roaming.

Before searching the location routing number, the initiation MSC canjudge whether the called user is a potential NP user first, which isspecifically as follows: if the directory number of the called user iswithin the range of a set inter-network roaming user number, then it isconsidered that the user is a potential NP user, or else, it is not apotential NP user. If the user is not a potential NP user, then processas a normal call ending flow; and if it is a potential NP user, processthe searching of the location routing number.

The above mentioned flow is described hereinafter in detail withreference to FIGS. 2-4.

FIG. 2 shows the procedure of a location registration conducted by themobile station. The MSC/VLR of the current roaming network of the doublemodule mobile station initiates a location registration request messageto the HLR of the present network (step 201), and the HLR sends theinter-network NP request message to the NPDB after receiving thelocation registration request message (step 202). The NPDB determineswhether to notify the original roaming network to logout theregistration according to the recorded current power on/off state of themobile station and the roaming network, if it is recorded in the NPDBthat the mobile station is in a power off state or the recorded roamingnetwork is the network that currently sends the inter-network NPrequest, then the procedure jumps to step 207; otherwise, the NPDB sendsan inter-network NP logout request message to the HLR of the originalroaming network of the mobile station, and notifies that the user hasroamed to other networks (step 203). The HLR of the original roamingnetwork sends the logout registration message to the MSC/VLR of theoriginal roaming network (step 204), after logouts the mobile station,the MSC/VLR of the original roaming network returns a logoutregistration response message to the HLR of the original roaming network(step 205). The HLR of the original roaming network returns aninter-network NP logout response message to the NPDB (step 206), thenthe NPDB records the current roaming network and active state of themobile station, and sends the inter-network NP response message to theHLR of the current roaming network (step 207), and the HLR of thecurrent roaming network sends a location registration response messageto the MSC/VLR of the current roaming network of the mobile station,thus completes the location registration of the mobile station (step208).

FIG. 3 is a flowchart shows that the mobile station is called whenroaming in the present network of the method according to the presentinvention. The initiation MSC/VLR sends a call request, the called useris a double module mobile station user, and the MSC/VLR searches theNPDB for the location routing number (step 301). The NPDB returns thelocation routing number to the initiation MSC/VLR according to thecurrent roaming network of the mobile station. In FIG. 3, in the casewhere the current roaming network of the mobile station recorded in theNPDB is the network that currently initiates the search request, theNPDB will return an empty response, and indicates the initiation MSC/VLRthat the called user is in the present network (step 302). Theinitiation MSC/VLR initiates a location search to the HLR of the presentnetwork (step 303), and the HLR of the present network completes thetransfer between a called routing number and a temporary local number,then the initiation MSC/VLR connects the call to the mobile station(step 304).

As shown in FIG. 4, in the flow that the mobile station is called whenroaming among different networks, first, the initiation MSC/VLRinitiates a call request, the called user is a double module mobilestation user, the initiation MSC/VLR searches the NPDB for the locationrouting number (step 401). The NPDB returns the location routing numberto the initiation MSC/VLR according to the current roaming network ofthe mobile station. In FIG. 4, the current roaming network of the mobilestation recorded in the NPDB and the MSC/VLR that currently initiatesthe search are not within the same network, and the NPDB returns thelocation routing number of the gateway office of the current roamingnetwork of the mobile station according to the location of the caller(step 402). The initiation MSC/VLR connects the call to gateway officeof the present network upon knowing that the mobile station is not inthe present network. If the call adopts ISUP signaling, then thedirectory number of the called user will be carried in parameter GenericAddress, and the address type is indicated as portable number, while thelocation routing number returned by the NPDB is carried in parameterCalled Party Number (step 403). The gateway office of the presentnetwork connects the call to the gateway office of the current roamingnetwork of the mobile station (step 404), and the gateway office of thecurrent roaming network initiates a location search to the HLR of thecurrent roaming network, thus the HLR completes the transfer between thecalled user routing number and the temporary local number (step 405).The HLR returns a response message, and the gateway office of theroaming network connects the call to the double module mobile station(step 406).

The method according to the present invention can not only be used forthe inter-network roaming between the GSM and CDMA, which of twocriteria, but also can be used in mobile networks of other criteria. Incase of the support of the mobile terminal, the present invention canrealize double networks roaming or multiple networks roaming of multiplecriteria networks.

While the present invention has been particularly shown and describedwith reference to the embodiments thereof, it will be understood bythose skilled in the art that any amendment or equivalent replacementmade to the technical solution of the present invention withoutdeparting from the spirit and scope of the present invention shall allbe covered by the scope of the claims of the present invention.

1. A method for a mobile station to roam among networks of differentcriteria, characterized in comprising: record user information in NPDB,wherein the user information includes a directory number and a locationrouting number of a mobile station, a mobile station identifier of themobile station that the mobile station signs at network 1, a mobilestation identifier of the mobile station that the mobile station signsat network 2, and the current NP state of the mobile station; when themobile station conducts location registration, the HLR of the currentroaming network conducts an inter-network NP request operation, thenreturns a location registration response message; when the mobilestation initiates a call, the call flow is the same as the currentinitiation flow; and when the mobile station ends the call, theinitiation switching center obtains the inter-network roaming state ofthe mobile station, and then conducts a call connection operation. 2.The method for a mobile station to roam among networks of differentcriteria according to claim 1, characterized in that the flow that themobile station conducts location registration specifically comprises:step 1, the switching center of the current roaming network initiates alocation registration request to the HLR of the present network afterreceiving the location registration request initiated by the mobilestation; step 2, the HLR of the current roaming network sends aninter-network NP request message to the NPDB; step 3, the NPDB judgeswhether it is necessary to notify the original roaming network of themobile station to conduct logout registration; and if not necessary, theflow proceeds to step 5; step 4, if it is necessary to notify theoriginal roaming network of the mobile station, the NPDB sends aninter-network NP logout request message to the HLR of the originalroaming network, then the HLR in turn sends a logout registrationmessage to the switching center of the original roaming network; afterreceiving the logout registration response message returned by theswitching center of the original roaming network, the HLR of theoriginal roaming network returns an inter-network NP logout responsemessage to the NPDB; step 5, the NPDB records the current NP state ofthe mobile station, and sends an inter-network NP response message tothe HLR of the current roaming network of the mobile station; and step6, the HLR of the current roaming network returns a locationregistration response message to the switching center of the presentnetwork.
 3. The method for a mobile station to roam among networks ofdifferent criteria according to claim 2, characterized in that the stepthat the NPDB judges whether it is necessary to notify the originalroaming network of the mobile station to logout the registration in thestep 3 further comprises: the NPDB determines whether to notify theoriginal roaming network to logout the registration according to therecorded current power on/off state of the mobile station and theroaming network, in the case where the mobile station recorded in theNPDB is in a power off state or the recorded roaming network is thenetwork that currently sends the inter-network NP request message, it isnot necessary to notify the original roaming network to logout theregistration; and in the case where the mobile station recorded in theNPDB is in a power on state and the recorded roaming network is not thenetwork that currently sends the inter-network NP request message, it isnecessary to notify the original roaming network to logout theregistration.
 4. The method for a mobile station to roam among networksof different criteria according to claim 1, characterized in that theprocedure that the mobile station ends the call specifically comprises:after receiving the call request, the initiation switching center checkswhether the called user is a potential NP user; and if the user is not apotential NP user,then process as a normal call ending flow; if the useris a potential NP user, then the initiation switching center searchesthe NPDB for the location routing number; the NPDB returns the locationrouting number to the initiation switching center, and the initiationswitching center completes the call connection according to the locationrouting number.
 5. The method for a mobile station to roam amongnetworks of different criteria according to claim 4, characterized infurther comprising: the initiation switching center checks whether thecalled user is a potential NP user first after receiving the callrequest; and if the user is not a potential NP user, then process as anormal call ending flow; if the user is a potential NP user, thesubsequent steps will be processed.
 6. The method for a mobile stationto roam among networks of different criteria according to claim 5,characterized in that the initiation switching center judges whether theuser is a potential NP user according to the directory number of themobile station, which is specifically as follows: if the directorynumber of the mobile station is within the range of a set inter-networkroaming user number, then the user is considered as a potential NP user,or else, the user is not a potential NP subscriber.
 7. The method for amobile station to roam among networks of different criteria according toany of claims 4-6, characterized in that the step that the initiationswitching center completes the call connection according to the locationrouting number further comprises: in the case where the location routingnumber is empty, it indicates that the mobile station and the initiationswitching center are in the same network, the initiation switchingcenter initiates a location search to the HLR of the present network,and the HLR of the present network completes the transfer between acalled routing number and a temporary local number, then the initiationswitching center connects the call to the mobile station; in the casewhere the location routing number is not empty, it indicates that themobile station and the initiation switching center are not in the samenetwork, and the location routing number is the location routing numberof the gateway office of the current roaming network of the mobilestation, the initiation switching center connects the call to thegateway office of the current roaming network of the mobile stationthrough the gateway office of the present network upon knowing that themobile station is not in the present network, and the gateway office ofthe current roaming network initiates a location search to the HLR ofthe current roaming network, the HLR completes the transfer between thecalled routing number and the temporary local number and returns alocation response message, then the roaming network gateway officeconnects the call to the mobile station.
 8. The method for a mobilestation to roam among networks of different criteria according to claim7, characterized in that when the initiation switching center connectsthe call to the gateway office of the current roaming network of themobile station through the gateway office of the present network, if thecall adopts ISUP signaling, then the directory number of the called useris carried in parameter Generic Address, and the address type isindicated as a portable number, while the location routing numberreturned by the NPDB is carried in parameter Called Party Number.
 9. Themethod for a mobile station to roam among networks of different criteriaaccording to claim 1, characterized in further comprising: when themobile station powers off, the HLR of the current roaming network of themobile station sends an inter-network NP deactive message to the NPDB,and the NPDB updates the NP of the mobile station in the network as thedeactive state.
 10. The method for a mobile station to roam amongnetworks of different criteria according to claim 1, characterized inthat the network 1 is the GSM network, and the network 2 is the CDMAnetwork.
 11. The method for a mobile station to roam among networks ofdifferent criteria according to claim 1, characterized in that thedirectory number of the mobile station in networks of different criteriais the same.
 12. The method for a mobile station to roam among networksof different criteria according to claim 1, characterized in that the NPstate of the mobile station comprises the roaming network and theactivate state of the mobile station.